Floating diode harmonic multiplier



United States Patent FLOATING DIODE HARD/IONIC MULTEPLIER James W.Battles, Riverside, Delbert E. Crane, Norco,

Robert W. Yancey, Riverside, and John R. Alday, Co-

rona, Califi, assignors to the United States of America as representedby the Secretary of the Navy Filed Aug. 26, 1965, Ser. No. 576,184 6@iaims. (ill. 32169) The invention herein described may be manufacturedand used by or for the Government of the United States of America forgovernmental purposes without the payment of any royalties thereon ortherefor.

The present invention relates to the generation of electromagneticenergy in millimeter wave bands, and more particularly to an improvedharmonic multiplier using a crystal diode.

Previous methods employed: klystron tubes which involved difficultconstruction, were expensive and easily damaged, had low efficiency,short life, and high frequency limitations; backward wave oscillatorsand traveling wave tubes which had limited frequency range, and wereexpensive and required expensive power supplies; and diode harmonicmultipliers which were of low efficiency and burnout power, unstable andeasily damaged, and required special and difficult to replace diodes aswell as external bias voltage.

The device of the present invention has: superior physical andelectrical stability; is less expensive than other commerciallyavailable devices; involves simple construction and uses replaceablecrystals; higher burnout powers and higher efiiciencies than heretofore;requires no external bias and has infinite shelf life. The instantdevice is highly useful in field environments, in any systems requiringmillimeter wave sources. It has many practical uses in local oscillatorsin millimeter wave receivers and radiometers; communication links; highresolution radar systems; missile guidance; and, in millimeter waveresearch.

It is an object of the present invention therefore, to provide a new andimproved harmonic multiplier for waveguides.

Another object of the invention is to provide an inexpensive harmonicmultiplier for waveguides that is easy to construct and simple toadjust.

A further object of the invention is to provide a harmonic multiplierfor waveguides that has very good efiiciency and stability.

Gther objects and many of the attendant advantages of this inventionwiil become readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

FIG. 1 is a cross-sectional view showing in detail the construction ofthe waveguide junction, probes and diode.

FIG. 2 is a typical graph showing the variation of the output pover ofthe harmonic multiplier as a function of the input power when using aheterojunction crystal diode.

The harmonic multiplier of the instant invention consists of twosections of microwave waveguide; one covering the frequency of thefundamental input frequency and the other covering the output harmonicfrequency, and joined with a coupling hole between the common sides.

As illustrated in FIG. 1, fundamental waveguide section 16 is covered byharmonic waveguide section 12, and are joined with a coupling hole 14-between them. In the particular embodiment illustrated in the drawingrectangular waveguide is shown and the waveguides are oriented similarto conventional crossguide configuration. A support 16 having anadjustable positioning device 17 with a dielectric post 18, of Lucite orthe like, is mounted on "ice fundamental waveguide 10, as shown.Dielectric post 18 supports a standard crystal microwave diode 20 with aharmonic probe extension 22 connected thereto. Harrnonic probe 22extends through coupling hole 14 into the harmonic waveguide 12.Dielectric post 18 supplies no electrical connection to the diode 20.

In the case of a heterojunction diode, as illustrated in the embodimentof FIG. 1, a fundamental probe extension 24 is also connected to diode20 and the diode is supported on post 18 by means of probe 24 which isconnected thereto. Probes extend in each direction in this instance,diode 2t) and fundamental probe 24 being within fundamental waveguide10, and harmonic probe 22 extending into harmonic waveguide 12.

Diode 20, with either one or two probes, is adjustably supported withinwaveguide 1%. In this device, diode 20 can be constructed external tothe waveguide or mount and then can easily be positioned and adjustedwithin Waveguide 18 by means of support 16 and adjusting device 17. Thediodes used in the present device, due to the constructionconfiguration, are able to withstand higher input powers thanheretofore.

In the configuration shown in FIG. 1, the fundamental energy is fed intowaveguide 14} where it is coupled into diode 20 by probe 24 and thenconverted into a harmonic of the fundamental. This harmonic is thencoupled into waveguide 12 by probe 22. The probe lengths are adjustedfor maximum harmonic output. The harmonic probe, 22, depth (i.e.,extension into harmonic waveguide 12) is adjusted by means of threadedadjusting device 17. Conventional adjustable shorts, not shown, can beused on each of the waveguides for matching purposes to maximize theoutput energy in a conventional manner.

The heterojunction diode shown in the illustrated embodiment of theinvention is shown merely by way of example and is not necessary for theoperation of the system. For the experimental data of FIG. 2, the metalprobes on the ends of diode 21} were cut so that probe 24 was a quarterwavelength of the fundamental and probe 22 was a quarter wavelength ofthe third harmonic and the diode was in a pill configuration.

The graph, FIG. 2, of the output of the harmonic multiplier as afunction of the input, shows that the efficiency of the device isincreased with higher input power. In this instance a gallium arsenidegermanium heterojunction diode was used. The fundamental frequency inthis mode was 9.86 gI-lz. and the klystron output power was 300milliwatts. However, in another mode, the fundamental frequency was 9.83gHz. and the maximum power available was 2 watts. An attenuator was usedto reduce the power to 300 milliwatts and tripler output of 6 mw. wasmeasured. This represents a 2mW. gain over the operation at 9.86 gHz.,but probably this was because the diode and holder were better matchedfor this frequency. The fundamental input power was then increased to520 mw. and the output increased to 8.6 mw.

The above power measurements were made with a dry calorimeter usingsuitable transitions. The length of the harmonic waveguide was such thatthe fundamental propagation was not detectable.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. A harmonic generator for waveguide frequencies comprising:

(a) a first section of waveguide for covering fundamental inputfrequencies,

(b) a second section of waveguide for covering output harmonicfrequencies,

(c) said first and second sections of waveguide being joined togetheralong adjacent sides thereof with a coupling aperture between commonsides,

(d) a microwave diode assembly having a crystal diode and at least oneharmonic probe extending therefrom,

(e) adjustable positioning means including a dielectric support beingmounted On an outside wall of said first Waveguide section foradjustably supporting said diode assembly on said dielectric supportwithin said first section of waveguide,

(f) said at least one harmonic probe extending through said couplingaperture into said second section of waveguide, wherein fundamentalenergy fed into said first section of waveguide is coupled into saiddiode and converted into a harmonic of the fundamental, and saidharmonic then coupled into said second section of waveguide by said atleast one probe.

2. A device as in claim 1 wherein the depth said at least one probeextends into said second section of waveguide is adjusted by saidadjustable positioning means, and said dielectric support supplies noelectrical connection to said diode.

3. A device as in claim 1 wherein said diode assembly can also be easilyremoved from said first section of waveguide for replacement andsubstitution by means of said adjustable positioning means.

4. A device as in claim 1 wherein the length of said at least one probeis adjusted for maximum harmonic output.

5. A device as in claim 1 wherein said microwave diode assembly includesa harmonic probe in addition to said at least one harmonic probeextending from said crystal diode in an opposite direction therefrom,the additional probe extending within said first waveguide section forcoupling fundamental energy fed into said first waveguide section intosaid diode.

6. A device as in claim 5 wherein the lengths of said probes areadjusted for maximum harmonic output.

References Cited UNITED STATES PATENTS 2,970,275 1/1961 KurZrOk 321693,246,266 4/1966 Racy 33383 3,311,839 3/1967 Rutulis 330-49 3,320,5165/1967 Lee 321-69 JOHN F. COUCH, Primary Examiner.

WARREN E. RAY, Examiner.

G. GOLDBERG, Assistant Examiner.

1. A HARMONIC GENERATOR FOR WAVEGUIDE FREQUENCIES COMPRISING: (A) AFIRST SECTION OF WAVEGUIDE FOR COVERING FUNDAMENTAL INPUT FREQUENCIES,(B) A SECOND SECTION OF WAVEGUIDE FOR COVERING OUTPUT HARMONICFREQUENCIES, (C) SAID FIRST AND SECOND SECTIONS OF WAVEGUIDE BEINGJOINED TOGETHER ALONG ADJACENT SIDES THEREOF WITH A COUPLING APERTUREBETWEEN COMMON SIDES, (D) A MICROWAVE DIODE ASSEMBLY HAVING A CRYSTALDIODE AND AT LEAST ONE HARMONIC PROBE EXTENDING THEREFROM, (E)ADJUSTABLE POSITIONING MEANS INCLUDING A DIELECTRIC SUPPORT BEINGMOUNTED ON AN OUTSIDE WALL OF SAID FIRST WAVEGUIDE SECTION FORADJUSTABLY SUPPORTING SAID DIODE ASSEMBLY ON SAID DIELECTRIC SUPPORTWITHIN SAID FIRST SECTION OF WAVEGUIDE, (F) SAID AT LEAST ONE HARMONICPROBE EXTENDING THROUGH SAID COUPLING APERTURE INTO SAID SECOND SECTIONOF WAVEGUIDE, WHEREIN FUNDAMENTAL ENERGY FED INTO SAID FIRST SECTION OFWAVEGUIDE IS COUPLED INTO SAID DIODE AND CONVERTED INTO A HARMONIC OFTHE FUNDAMENTAL, AND SAID HARMONIC THEN COUPLED INTO SAID SECOND SECTIONOF WAVEGUIDE BY SAID AT LEAST ONE PROBE.